Lithium-ion batteries are secondary batteries having high energy density and are used as power sources for portable devices, such as a notebook computer or a cell phone, utilizing the characteristics thereof.
In recent years, as a power source for an electronic device, a power source for power storage, a power source for an electric car, etc., for which movement toward higher performance or downsizing is advancing, a lithium-ion battery offering high input-output property, high energy density, and long operating life has drawn attention.
For example, in Japanese Patent Publication (JP-B) No. 4196234, a battery using a cathode active material with a spinel structure having a lithium occlusion and release potential of from about 4.7 V to about 4.8 V with respect to Li/Li+ in a cathode, and using, as an anode active material, titanium oxide with a spinel structure having a lithium occlusion and release potential of about 1.5 V with respect to Li/Li+, has been studied from a viewpoint of achieving a high energy density and a longer operating life. In the battery, increase in an energy density of the battery has been achieved by using an active material which is capable of increasing a potential in a state of charge as a cathode active material. Meanwhile, since a potential of an anode in a state of charge is as high as about 1.5 V with respect to Li/Li+, the activity of lithium occluded in a molecular structure in a state of charge is low, and the reduction of an electrolyte is suppressed. Further, even when a solvent, a supporting electrolyte salt, or the like which composes the electrolyte is a compound containing oxygen, since the anode active material is an oxide, an action to generate an oxide coating film at an interface of the electrolyte through a reaction between them can be reduced, and self-discharge of the battery is suppressed.